AU2005306515B2

AU2005306515B2 - Device to treat liquid and foam

Info

Publication number: AU2005306515B2
Application number: AU2005306515A
Authority: AU
Inventors: Joseph Charpentier; Michel Durris; Johny Hector Haegeman; Bruno Poot
Original assignee: Aquasystems Int N V; Aquasystems International NV; OTV SA
Current assignee: Aquasystems International NV; Veolia Water Solutions and Technologies Support SAS
Priority date: 2004-11-22
Filing date: 2005-11-22
Publication date: 2010-08-12
Anticipated expiration: 2025-11-22
Also published as: RU2374186C2; US7744679B2; US20080314247A1; AU2005306515A1; EP1812351A1; CN101084165A; WO2006053408A1; BRPI0518331A2; RU2007118471A

Description

DEVICE TO TREAT LIQUID AND FOAM Field of the invention The invention relates to foam breaking equipment for treating an aqueous medium volume with floating foam. 5 The prior art Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field. An aeration device for introducing gas in a liquid such as wastewater of an activation 10 basin is disclosed in US 4,290,885. The device is placed in a tank. Said tank comprises a vertical tube with a top opening and a bottom opening, a propeller is mounted at the top of the tube so as to push water or liquid downwardly. An air conveying tube is provided, so that by the depression or suction created by the pushing propeller, air is sucked. Said air after passing through the propeller is pushed downwardly. A cap is provided above 15 the top opening so that only liquid can pass in the cylinder. A drawback of such a system is that air can stay in the cylinder and form big bubbles, which could be detrimental for a correct working of the propeller and/or causes damages at the propeller. Other aerating devices are known, such as AQUA TURBO® devices sold by applicant. All these devices were unable to treat correctly the foam layer floating at the surface of 20 the volume. Brief description of the invention According to a first aspect, the invention provides foam breaking equipment for a system for treating an aqueous medium volume with floating foam, contained in a tank having a bottom and an upper portion, whereby said foam breaking equipment comprises: 25 - a foam conveying means with at least one inlet and one outlet, - a sucking means comprising a screw or helical centrifugal impeller and adapted for creating a downwards suction of fluid in the conveying means from the inlet -2 towards the sucking means, whereby the distance separating the inlet from the sucking means or the outlet is at least 40cm, - a means adapted for breaking and/or disturbing the foam extending above the inlet and/or in front of the inlet, whereby said means for breaking or disturbing the 5 foam is an pipe extending at least partly in the conveying means and adapted to extend at least partly at a level above the foam, and whereby the pipe is provided with a channel with a first opening adapted to be located above the foam level and a second opening extending at least 20cm below the level of the inlet of the conveying means, said channel being adapted for the exhaust of gas released in the conveying means. 10 Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to". Advantageously, the inlet has a surface of passage or opening adapted for the passage of 15 floating foam, especially a thick foam, such as foam with a density greater than 0.05, preferably greater than 0.1, such as greater than 0.15, 0.20, 0.25, etc. The inlet is advantageously provided with means for controlling the flow of floating foam into the conveying means and/or a means for controlling the overflow of foam towards the conveying means. For example the conveying means is associated to a foam overflow 20 system, the position of which can be regulated or adapted via a regulation system. Such a regulation system can for example adapt the position of the overflow level relative to the position of the sucking means, in function of the upper foam level. According to a preferred embodiment, the sucking means is adjacent to the bottom of the tank or attached to the conveying means so as to extend adjacent to the lower portion of 25 said conveying means. However, it can also be located at any other position or level in the tank. According to a detail of a preferred embodiment, the system comprises a means for admitting a gas and/or liquid in the conveying means below the level of the inlet and/or at the level of the sucking means.

-3 According to another embodiment, the inlet has a surface of passage adapted for the passage of floating foam, whereby said inlet comprises a means adapted for breaking and/or disturbing the foam extending above the inlet or in front of the inlet. Said means is advantageously also a means guiding the foam in a portion of the conveying means. 5 Preferably, the means for breaking the foam is an element extending at least partly in the conveying means and adapted to extend at least partly at a level above the foam. Advantageously, the element extends in the conveying means on a length of at least 10 cm, preferably from 20cm to 100cm. Preferably, the conveying means in its portion where the element extends has a 10 substantially ring or annular passage for foam or a passage defined between a first (advantageously cylindrical) wall and a second (advantageously cylindrical) wall, the second wall extending at least partly in the volume defined by the first wall. The conveying means can be further be provided with one or more distinct foam breaking systems located between the inlet and the outlet of the conveying means. According to 15 an embodiment, the pipe is provided with a channel with an inlet adapted to be located above the foam level and an outlet extending at least 10cm, advantageously at least 20cm below the level of the inlet of the conveying means, said channel being adapted for the passage of exhausting gas from the conveying means. When gases have to be expelled, it can be advantageous to provide the system with a gas 20 suction means, such as a propeller, a fan or a gas sucking means driven into rotation by the wind. The surface of passage of the channel for gas exhaust is advantageously comprised between 0.1 and 0.5, preferably between 0.25 and 0.4 times the surface of passage of the portion of the conveying means adapted for foam which is adjacent to the sucking 25 means. Preferably, the pipe is provided with a system for controlling the passage of gas through the channel. According to a preferred embodiment, the equipment comprises a funnel shaped element adapted for conveying foam towards the opening of the conveying means or duct, 30 whereby said funnel shaped element is associated to level regulating system adapted for -4 controlling the level of foam flowing in the funnel shaped element by overflow. For example the funnel shaped element is associated to a fixation element or a positioning system enabling a regulation or control of the overflow level. The foam flows then towards the opening of the conveying means, which is provided with a means adapted 5 for breaking and/or disturbing the foam present above the inlet or in front of the inlet. According to another embodiment, the equipment comprises a means adapted for controlling the pressure in the conveying means. According to an advantageous embodiment, the conveying means has one or more inlets defining a total inlet surface adapted for receiving foam and defines a chamber guiding 10 the fluid and/or foam towards the sucking means, whereby said chamber has at least a portion with a surface of passage greater than said total inlet surface for foam, said portion being adjacent to the sucking means. Advantageously, said portion of the chamber with an enlarged surface of passage has a surface of passage comprised between 1.1 and 5, preferably between 1.2 and 2 times the 15 total inlet surface adapted for receiving foam. Preferably, the foam is conveyed in the conveying means in at least two portions, a first portion or upper portion adjacent to the inlet or inlets for receiving foam and a second or lower portion adjacent to the sucking means, whereby the second portion has a surface of passage comprised between 1.05 and 5, preferably between 1.2 and 2 times the 20 surface of passage of the first portion. According to a further detail of said preferred embodiment, the chamber comprises at least a third portion intermediate between the first (or upper) and the second (or lower) portion, said third portion having a surface of passage greater than the surface of passage of the first portion, but lower than the surface of passage of the second portion. 25 The surface of passage of one or another portions is calculated in a plane perpendicular to the flow direction of the foam. According to an advantageous embodiment, the conveying means comprises inner wall and is associated to a means for admitting some liquid, in particular some liquid from the bath to flow at least partly along said inner wall of the conveying means. Such a flow -5 seems to be advantageous for the downwards movement of the foam towards the sucking means. When the conveying means comprises two portions (a lower and an upper) which are mobile the one with the other, whereby one portion extends at least partly in the hollow 5 space of the other portion, and whereby spaces or channels are formed between the inner wall of one portion and the outer wall of the other portion, said channels or spaces being adapted for enabling a flow of liquid into the conveying means, said liquid flowing then at least partly along the inner wall of the lower portion. According to detail of preferred embodiments: 10 - the suction means comprises most preferably with a double helix impeller, and/or - the conveying means has at least one wall defining a chamber in the volume, said chamber being adapted for communicating substantially only with the volume through the inlet and through its outlet via the suction means, and/or - a means is adapted for conducting at least one chemical additive or reactive in the 15 chamber, and/or - at least partly the conveying means is mobile with respect to the tank, whereby at least preferably the upper portion of the conveying means is mobile with respect to the tank, and/or - at least the upper portion of the conveying means is mounted on a floating 20 element, and/or - the suction means is associated to a driving motor located in the tank or adapted for extending above the liquid level of the volume to be treated, and/or - the system further comprises a sprinkler system and/or an anti-foam dosing system and/or a mixer and/or a submersible aerator. 25 According to a specific embodiment, the pipe for gas exhaust is an open tube provided at its lower end engaged in the conveying means with lateral openings or openings in its lateral wall. The lower end of said open tube can also be enlarged (such as a reverse funnel shape).

-6 According to a specific embodiment, the pipe extending at least partly in the conveying means is an open tube which is mobile with respect to at least a portion of the conveying means, whereby the position of the pipe can be adapted, for example controlled. According to a detail of said specific embodiment, the conveying means comprises at 5 least two portions movable the one with respect to the other, whereby the pipe is attached to one of said portions of the conveying means. Preferably, the conveying means comprises an upper portion and a lower portion, the upper portion being movable with respect to the lower portion, whereby the element is attached to the upper portion and whereby a means is adapted for adjusting the relative position of the upper portion 10 with respect to the lower portion and a means is adapted for maintaining said relative position between the lower and upper portions. Advantageously, the upper portion is provided with a funnel shaped element guiding the foam towards the foam receiving inlet of the conveying means. The lower portion is advantageously mounted on a floating support. The suction means can be completely in the conveying means, 15 completely out of the conveying means or partly in and partly out of the conveying means. According to a second aspect the invention provides a treatment installation comprising at least one tank adapted for containing an aqueous liquid medium with floating foam, and a foam breaking equipment according to any one of the claims 1 to 18 adapted for 20 sucking floating foam, defoaming foam in the conveying means, exhaust of gas released by the defoaming in the foam conveying means and recycling foam into an aqueous liquid medium. Other details and characteristics of the foam breaking equipment and conveying means of the invention are disclosed in the description of the system of the invention. 25 The invention relates further to a treatment installation comprising at least one system of the invention. According to a third aspect, the invention provides a process for breaking foam floating on an aqueous liquid medium in which floating foam is broken in a foam breaking equipment of the first aspect, or of a treatment installation of the second aspect.

-7 In the invention, the conveying means can be a tube or piping system which can be conical, truncated cone, cylindrical, flared, combinations thereof The cross section can also be square, rectangular, octagonal, hexagonal, etc. The conveying means in the system of the invention can be used for various purposes, 5 such as mixer, aerator, floatable re-entrainer, foam aspirator and combinations thereof. When gas is exhausted from the conveying means, the upper end of the conveying means can be provided with gas suction means, such as an impeller, a fan, etc. The liquid possibly admitted in the conveying means can be liquid from the water treatment volume or from another water treatment tank, such as a hydrolysis tank. The 10 liquid is advantageously introduced under pressure, for example by means of one or more jets, hydrojets, or by simple gravity. The conveying means can be made in various material. Preferably, the material used will be such that the face in contact with the foam will be water repellent and/or with anti adhesion properties. The inner surface of the conveying means or pipe, especially its 15 upper portion adjacent to the inlet can be provided with blades or fins so as to cut or further disturb the foam passing into the conveying means. Details and characteristics of preferred embodiments will be disclosed in the following description in which reference is made to the attached drawings. In said drawings, 20 Fig. 1 is a schematic view of a liquid/foam (for example water/foam) treatment tank (not according to the invention), Fig. 2 is a cross section view along the line II-II in the tank of Fig. 1, Fig.3 is a schematic of another embodiment not according to the invention, Fig. 4 is a cross section view along the line IV-IV in figure 3, 25 Fig. 5 is a schematic view of a first embodiment according to the invention, Fig. 6 and 7 are cross section view along the lines VI-VI and VII-VII in said first embodiment of the invention, Fig. 8 is a schematic view of a second embodiment of the invention, Fig. 9 and 10 are schematic views of third and fourth embodiments of the invention, -8 Fig. 11 is a detail view of the means for exhausting a gas from the conveying means used in the embodiments of figures 9 and 10, Fig 12 is a schematic view of a fifth embodiment of the invention, Fig. 13 is a schematic view of an installation of the invention, 5 Fig. 14 is a schematic view of a sixth embodiment of the invention, Fig 15 is a cross section view along the line XV-XV, Fig. 16 is a cross section view along the line XVI-XVI, Fig. 17 is a partial perspective view of a detail of Figure 14, Fig. 18 is a schematic view of a seventh embodiment of the invention, 10 Fig 19 is a further schematic view of a foam breaking equipment of the invention in a tank, and Fig 20 is a view of the foam breaking equipment of figure 19 with adapted piping system. Figure 1 is a schematic view of a system for treating an aqueous medium volume with 15 formation of a thick and dense floating foam layer. The volume B comprises a solid or substantially solid layer deposited on the bottom 2 of the tank 1, a liquid layer with material or bacteria or other microorganism in suspension, and a thick and dense foam layer floating on the liquid layer. The foam is floating in the upper portion 3 of the tank 1. A pipe 4 in PVC with an inner silicon coating (other materials can be used, such as 20 steel, stainless steel, aluminum, etc.) extends between an inlet 5 located in the upper portion 3 (i.e. in the foam layer) and an outlet 6 adjacent to the bottom 2 or to a lower portion of the volume. A suction means 7 (in the form of a motor 7A driving into rotation a double helix centrifugal impeller 7B (screwpeller@ sold by Aquasystems International NV, Belgium). The suction means 7 is adapted for sucking the fluid (in the 25 form of foam) present in the pipe 4 and for projecting and mixing said sucked foam with liquid present in the bottom of the tank. A water circulation C is so created in the volume B. The foam falls in the pipe 4, as said pipe is in depression and is moved downwardly. The liquid level in the pipe 4 corresponds advantageously to substantially the upper level of the impeller 7B. The distance D between the inlet 4 and the suction means 7 is 30 advantageously of at least 40, preferably more than 50cm, most preferably more than 100cm, such as 200cm or even more such as 300cm, 400cm, 500cm, etc.

-9 In order to facilitate the flow of foam in the pipe 4, the pipe is provided at its inlet with an element or a rod 10 attached to the pipe by several plates I1 extending at least partly vertically. The element 10 has advantageously a diameter of more than 2cm and extends partly in the pipe (for example on a length of 20 to 50cm, and partly outside of the pipe 4 5 (preferably at least partly above the foam layer). The top of the element 10 can be used as means for detecting when the foam layer is at a level above an admissible level. The element 10 and the plates 11 act as means for disturbing the foam layer, whereby facilitating the suction of the foam in the pipe 4. The rod 10 reduces also the section of passage of the pipe 4 near its inlet 5 with respect 10 to the section near the impeller 7B. The foam falling from the portion in which the rod 10 extends falls thus in a zone with a larger section of passage. Figure 3 is a view similar to that of figure 1, except that another impeller 7B is used, that the motor 7A is mounted on a floating support 12. The floating support bears the pipe 4 by means of pieces 13 enabling to adjust the relative vertical position of the inlet 5 with 15 respect to the floating support 10 and thus with respect to the foam layer. The rod 15 driven in rotation by the motor 7A extends in the pipe and acts as means for breaking the foam layer at the inlet 5 and in the pipe 4. The rod is advantageously provided with a small helical screw adapted for creating a downwards movement of compounds present on the rod or in contact with the rod 15. The pipe 4 is provided near its inlet 5 with a 20 series of inner fins 16 so as to break the foam layer. By adapting the level of the inlet 5, it is possible to use the system as a simple mixer (inlet at a level below the foam layer), a system for ensuring a correct treatment of the foam layer (inlet in or adjacent to the foam layer), and as an aerator (inlet above the foam layer). Figure 5 is a view of an embodiment similar to that of figure 1, except that the rod 10 25 has been replaced by a pipe 17 so as to remove gas from the pipe 4 (gas generated by the defoaming of foam in the pipe 4), and that the pipe 4 is provided with an additional foam breaking equipment 18 distant from the foam breaking equipment formed by the plates 11. Figure 8 is a view of an embodiment similar to that of figure 5 except that a gas (air, 30 oxygen enriched air, oxygen, etc.) is introduced in the pipe at the level of the impeller 7B. Said gas, for example gas with a pressure of I to 10 10' Pa, is issued from a gas - 10 compressor 18 and conveyed to the pipe 4 by the flexible duct 19. Such an air/oxygen inlet increases the oxygenation of the treatment bath. Figures 9 and 10 are views of embodiments similar to the embodiment of figure 5, except that a propeller (submersible propeller used for aerating a volume, such as AQUA 5 TURBO@ sold by Aquasystems International NV, Belgium)is used instead of a screw impeller, and that the lower end 20, 21 of the pipe 17, 17A is provided with means for controlling the exhaust of gas from the pipe 4. When gases have to be exhausted, the fact to have exhausted pipes with lower openings located at different level, enables to have a better control of the gas exhaust during the downwards flow of the foam in the pipe 4, 10 whereby ensuring a better downwards flow of the foam. When gas or liquid are admitted in the pipe 4, the lower end 20, 21 of the pipe 17, 17A is provided with a cap 22 (see figure 11). The cap 22 has a series of small channels 23 adapted for the passage of gas (air, oxygen, nitrogen, etc.) in the form of jets. Advantageously, the gas in the pipes is pressurized gas. 15 In the embodiment of figure 10, two gas pipes 17, 17A are used, the bottom of the pipe 17A being at a level lower than the level of the bottom of the pipe 17. This enables to control the exhaust of air or gases in function of the level. Figure 12 is a view of an embodiment similar to that of figure 5, except that the suction means 7 is a submersible aerator with a diffusion head 24. 20 Figure 13 is a view of an installation of the invention. Said installation comprises a tank 30 provided with an inner wall 31, so as to define two distinct reservoirs 32, 33. A screw impeller 7B driven in rotation aspires foam from the foam layer of reservoir 32 through the inclined tube 34 and mixes said foam with the content of the reservoir 33. The upper portion of the tube 34 is provided with a tube 17 enabling a gas exhaust due to the gas 25 released when the defoaming or partial defoaming of the foam. Foam of the reservoir 33 or compound issued from said foam can be recycled in the reservoir 32 by overflow above the inner wall 31. This installation enables two have two distinct zones of treatment. The zone of treatment of reservoir 33 being for example a zone where various additives or microorganisms are - 11 added for a better treatment of the fat present in the foam, as well as other materials or compounds, especially compounds or materials floating on the liquid bath or low density materials. Each zone or reservoir 32, 33 can be provided with various means, such as mixer, 5 aerator, sprinklers, anti-foaming dosing, floattable re-entrainer, submersible aerator, inlet pipe, outlet pipe, device (with screw) for removing sinking solids, etc. Possibly the upper portion of the pipe 4 or tube 34 is mobile with respect to the tank 1 or reservoir 30, said portion being then mounted on a floating support and connected via a flexible pipe to the pipe 4 or the tube 34. 10 Figure 14 is a view of a system similar of figure 5, except that the suction means is located above the bottom 2, for example at a layer sufficient for having no or a gentle agitation at the bottom level. The top of the pipe 4 is provided with a cap 30 suitable for bearing the pipe 17. The cap 30 has openings 31 defined between radial arms 32 provided with flaps 33. 15 Figure 18 is a view of a further embodiment in which the conveying means 4 has a shape of a truncated cone, the top thereof being directed upwardly. The suction means is mounted on a support 35 adapted for modifying the position of the screw so that the screw is completely in the pipe 4 (dashed line DAI), completely outside the pipe 4 (screw DA2), or partly in and out. 20 Figure 19 is a schematic view of a foam breaking equipment of the invention in a system of the invention. Said system comprises a tank adapted for containing a liquid or substantially liquid medium or suspension, on which a dense and thick foam layer floats. Said tank is provided with a foam breaking equipment 100 adapted for recycling and breaking foam into the liquid medium, for example floating or close to the bottom 2 of 25 the tank 1. The foam breaking equipment 100 comprises: - a floating support 102; - 12 - a substantially vertical piping system 103, said piping system comprising an lower portion 103 A attached to the floating support 102, and an upper portion 103B mobile with respect to the lower portion 103 A. The upper portion 103B is partly engaged in the channel of the lower portion 103 A. The upper end of the 5 upper portion 103B is provided with a funnel shaped extension 104 adapted for guiding foam towards the upper annular opening 105 of upper portion 103B. - a means 120 for adapting the position of the funnel shaped extension 104 with respect to the floating support 102, whereby adapting the position of the second portion 103B of the piping system, with respect to the lower portion 103 A of 10 said piping system. Said means is also advantageously a means for maintaining or for controlling a specific position, for example for ensuring that substantially only the top surface of the foam layer is flowing in the extension 104 towards the opening 105. - a pipe 106 attached to the upper portion 103B and/or to the extension 104 and/or 15 to an extension of the floating support, so that a portion of the pipe 106 extends within the lower portion 103 A and below (outside) said lower portion 103 A, while another portion of the pipe 106 extends through the funnel shaped extension 104 and above said extension 104. The upper opening 107 of the pipe 106 is adapted for extending above the foam layer, while the lower opening 108 20 of the pipe extends in the lower portion 103 A .Between the outer wall of the upper portion 103B and the inner wall of the lower portion 103 A, one or more channels are formed for the flow of liquid. The upper edge of the lower portion 103 A is adapted for extending with in the liquid phase, i.e. below the foam phase. This or these channels ensure a flow of liquid from the treatment bath 25 along at least a part of the inner wall of the lower portion 103A. - a sucking means, advantageously a screw impeller 107, preferably a double helix centrifugal impeller, adapted for sucking liquid and/or foam from the lower portion 103 A and expelling said liquid and foam back into the liquid treatment bath. The helix shaped blade extends at least partly in the lower portion 103 A. 30 Said impeller is for example attached to the lower portion 103 A and to the floating support 102.

-13 In said configuration, the piping system 103 defines a channel for the flow of foam towards the bottom, said channel comprising at least the three following portions: - an upper portion 110 with an annular surface of passage SI defined between the inner cylindrical wall of the upper portion 103B of the piping system and the 5 outer wall of the gas exhaust pipe 106, - a lower portion 111 with a circular surface of passage S2 defined by the inner wall of the lower portion 103A of the piping system, said lower portion 111 extending below the lower opening 108 of the pipe 106, and - an intermediate portion 112 extending between the lower and upper portions 10 111,110, said intermediate portion having a substantially annular surface of passage S3 defined between the inner wall of the lower portion 103A of the piping system and the outer wall of the gas exhaust pipe 106. The surface of passage S2 is advantageously comprised between 1.05 to 1.5 times the surface of passage SI, while the surface of passage S3 is greater than SI, for example 15 equal to 1.01 to 1.1 times S1. The pipe 106 has a surface of passage for gas which corresponds to substantially 0.1 to 0.5 times S2. Larger surface of passage is possible for the pipe 106. The pipe 106 enables the exhaust of gas released during the at least partial defoaming of foam inside the piping system 103, especially at the place of its enlargement (portion I 11), whereby 20 increasing the efficiency of the recycling of foam and components issued from said foam into the liquid bath. Rods 120 are used for adapting the position of the funnel shaped extension 104, said rods acting moreover as means for breaking the foam flowing into said extension 104. Said embodiment has the following advantages: 25 - by using the helix blade turbine or impeller, greater sucking forces are induced in several directions, especially in directions enabling a good suction and a good distribution and movement in the liquid bath. - the adjustment of the upper portion 103B with respect to the lower portion 103A is carried out by simple sliding movement, whereby the position of the upper 30 edge of the funnel shaped extension 104 can be precisely adapted in function of - 14 the height of the foam layer and whereby the position of the impeller in the bath under the liquid level is substantially not modified. Figure 20 shows the foam breaking equipment 100 with the upper portion 103B in an upwards position with respect to its position in figure 19. 5 The systems and installations of the invention can be used for various treatments, such as treatments of manure waste, animal liquid manure, industrial liquid waste, water treatment system, lagoons, liquid waste issuing from the food industry, etc. The working of the foam breaking equipment can be controlled in function of several parameters, such as thickness of the foam layer, upper level of the liquid layer, 10 oxygenation level, biodegradation, temperature, structure of the foam, etc. For example, such a control can be controlled by a computer system receiving signal(s) from one or more sensors. The speed of the impeller or sucking means can be controlled, for example in function of the agitation required for ensuring a good breaking of the foam and its good dispersion 15 in the liquid, for ensuring a good suction of the foam (for example in function of its density and structure, in function of the distance between the top level of the foam layer with respect to the position of the sucking means), etc. The foam breaking equipment unit can also be controlled so as to suck and break foam from a specific zone. For example, only the top layer of the foam is suck and treated. For 20 said purposes, a foam overflow system can be used, said foam overflow system enabling only the top foam layer above a specific level to flow in the foam breaking equipment unit. Said specific overflow level can be controlled, automatically or not, in function of various parameters, such as foam density, foam thickness, minimum/maximum admissible foam flow rates, etc. 25 Such a control can be carried out by a computer, for example acting on the rod or driving the rod 120 so as to move upwardly or downwardly the funnel shaped element 104. In the system, especially the foam breaking equipment of the invention, the length of the conveying means as well as the position of the element 106 in said conveying means can also be controlled. Such a control is for example carried out in function of the defoaming - 15 zone of the foam in the conveying means or the upper level at which a sufficient defoaming of the foam starts.

Claims

1. Foam breaking equipment for a system for treating an aqueous medium volume with floating foam, contained in a tank having a bottom and an upper portion, whereby 5 said foam breaking equipment comprises: - a foam conveying means with at least one inlet and one outlet, - a sucking means comprising a screw or helical centrifugal impeller and adapted for creating a downwards suction of fluid in the conveying means from the inlet towards the sucking means, whereby the distance separating the inlet from the sucking 10 means or the outlet is at least 40cm, - a means adapted for breaking and/or disturbing the foam extending above the inlet and/or in front of the inlet, whereby said means for breaking or disturbing the foam is an pipe extending at least partly in the conveying means and adapted to extend at least partly at a level above the foam, and whereby the pipe is provided with a channel 15 with a first opening adapted to be located above the foam level and a second opening extending at least 20cm below the level of the inlet of the conveying means, said channel being adapted for the exhaust of gas released in the conveying means.

2. The foam breaking equipment of claim 1, in which the exhaust gas pipe defines a channel with a surface of passage for exhausting gas from the foam conveying means 20 comprised between 0.1 and 0.5, preferably 0.25 and 0.4 times the surface of passage of the portion of the foam conveying means adjacent to the sucking means.

3. The foam breaking equipment of claim 1, in which the sucking means comprises a double helix impeller.

4. The foam breaking equipment of claim 1, in which the sucking means is mounted 25 on a support adapted for modifying the position of the screw with respect to the foam conveying means.

5. The foam breaking equipment of claim I, in which the exhaust gas pipe extends in the foam conveying means on a length from 20 to 100cm.

6. The foam breaking equipment of claim 1, in which the sucking means is adapted 30 at a level such that the difference between the level of the foam inlet in the foam -17 conveying means and the level of the sucking means is at least 40cm, advantageously at least 100cm, preferably more than 150cm.

7. The foam breaking equipment of claim 1, in which the sucking means is adapted for being adjacent to the bottom of the tank or is attached to the foam conveying means 5 so as to extend adjacent to the lower portion of said foam conveying means.

8. The foam breaking equipment of claim 1, in which the gas exhaust pipe reduces the section of passage of the foam conveying means with respect to the section of passage adjacent to the sucking means, so that foam falls from a portion of the conveying means in which the gas exhaust pipe extends into a portion with a larger 10 section of passage.

9. The foam breaking equipment of claim 1, which comprises a means adapted for admitting a gas in the foam conveying means below the foam inlet and/or at the level of the sucking means.

10. The foam breaking equipment of claim 1, in which the foam inlet comprises 15 means adapted for breaking and/or disturbing the foam extending above the foam inlet or in front of the foam inlet.

11. The foam breaking equipment of claim 1, in which the foam conveying means comprises a wall adapted to define a chamber in the aqueous medium with floating foam, said chamber being adapted for communicating with the aqueous medium 20 substantially only via the foam inlet and the outlet of the foam conveying means, and in which the foam breaking equipment comprises means adapted for conducting at least one chemical additive or reactive in the chamber defined by the wall of the foam conveying means.

12. The foam breaking equipment of claim 1, in which the foam conveying means is 25 adapted for being mobile with respect to the tank containing the aqueous medium with floating foam, whereby the foam conveying means advantageously comprises a lower portion and an upper portion adapted for being mobile with respect to the tank, at least the upper portion being preferably mounted on a floating element. -18

13. The foam breaking equipment of claim 1, in which the sucking means is associated to a driving motor adapted to be located in the tank or above the liquid level in the tank.

14. The foam breaking equipment of claim 1, in which the foam conveying means 5 comprises two portions mobile the one with respect to the other.

15. The foam breaking equipment of claim 14, which comprises an upper portion provided with a funnel shaped extension, a lower portion and at least one means for adjusting the position of the upper portion with respect to the lower portion and for maintaining said position. 10

16. The foam breaking equipment of claim 14, in which the upper portion is partly engaged in the channel formed by the lower portion, whereby between the outer wall of the upper portion and the inner wall of the lower portion, one or more channels are formed for the flow of liquid.

17. The foam breaking equipment of claim 12, in which the lower portion adjacent to 15 the sucking means has a surface of passage comprised between 1.05 and 5, preferably between 1.2 and 2 times the surface of passage for foam of the upper portion.

18. The foam breaking equipment of claim 1, which comprises a means adapted for controlling the pressure in the foam conveying means.

19. A treatment installation comprising at least one tank adapted for containing an 20 aqueous liquid medium with floating foam, and a foam breaking equipment according to any one of the claims 1 to 18 adapted for sucking floating foam, defoaming foam in the conveying means, exhaust of gas released by the defoaming in the foam conveying means and recycling foam into an aqueous liquid medium.

20. The treatment installation of claim 19 comprising at least a first reservoir tank 25 adapted for containing an aqueous liquid medium with floating foam, a second tank adapted for containing an aqueous liquid medium, and a foam breaking equipment with its foam inlet open in the first tank and its outlet open in the second tank, said foam breaking equipment being adapted for sucking foam from the first tank and recycling foam in the second tank. -19

21. A process for breaking foam floating on an aqueous liquid medium in which floating foam is broken in a foam breaking equipment of any one of the claims I to 18, or of a treatment installation of claim 19 or 20.

22. Foam breaking equipment substantially as herein described with reference to any 5 one of the embodiments of the invention illustrated in the accompanying drawings and/or examples.

23. A treatment installation substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples. 10

24. A process for breaking foam floating on an apparatus liquid medium substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples.